Ignition wiring help please

db · Post by db » Thu Jul 10, 14 4:42 pm

I'm swapping my old FBO box for a Mallory with the all-important rev-limiter!
Ist pic is how it's worked up to now
2nd pic is the Mallory instructions
3rd pic is how I think the new wiring should go

Does it look right? What should I connect the Field wire from the alternator now?

Guy · Post by **Guy** » Fri Jul 11, 14 6:22 am

Looks ok to me, just make sure the the wire from the ignition switch stays 12v when switch between start and run.

morgan · Post by **morgan** » Fri Jul 11, 14 9:06 am

I cant see the direct 12V feed to your coil - mallory diagram implies that there should be constant 12v from ign, but your sketch shows only the mallory plug ?

Just been through similar with mine (ripping out all the mopar orange box stuff) and essentially, so long as the ECU and coil get their 12v on start and run (not the 8v that ballast would give) all is cool.

Might be my interpretation of your sketch though.

db · Post by db » Fri Jul 11, 14 11:23 am

Thanks - Top centre of my drawing, the red goes to batt+ , black goes to earth, so that's all good

How about the field wire from the alternator?

Dave999 · Post by **Dave999** » Fri Jul 11, 14 11:40 am

i'm with morgan

looks like a swicthed 12 volt goes to the coil+ and that is missing from your diagram

bang in the middle of the mallory one

dunno how vlital it is

Guy · Post by **Guy** » Fri Jul 11, 14 4:51 pm

Yup i missed that

db · Post by db » Fri Jul 11, 14 11:49 pm

Ah, no! I see what your thinking.. the 'connection' on the + side of the coil is actually an insulator!
That threw me too but then I noticed the arrow (above left from coil) labelled INSULATED CABLE BLOCK.
So- only the yellow is actually connected to the coil+
The ign +12v red, Mallory red and 'all other wires, etc' are connected together at the coil but NOT connected TO the coil!

Still dunno where the alt field wire goes though!

db · Post by db » Mon Jul 14, 14 11:35 am

Still need help with the FIELD wire.... anyone?

Dave-R · Post by **Dave-R** » Mon Jul 14, 14 11:40 am

Your field wire just needs to hook up to the switched 12v source from your ignition switch.

I take it you have an internally regulated alternator?

db · Post by db » Mon Jul 14, 14 11:41 am

Splendid cheers!

Dave-R · Post by **Dave-R** » Mon Jul 14, 14 11:43 am

I just expanded my answer.

morgan · Post by **morgan** » Mon Jul 14, 14 12:05 pm

Hang on - you must make sure you grasped what dave said there - alternator needs regulator somewhere. The 'black box' on your old setup did this - but your alternator looks different...

Old alternators just had the two connections on them, yours has 3 ?? - the ol' "dual field alternator" (it isnt really, but they tend to get called that).

Point is, your alternator should run a voltage regulator and I cant see it on your diagram.

Either run the same as your old one, or modify to this type (diagram) which is what I did for mine. Either would do it. Your field wire then taps back in to the system where the ballast used to be (i.e. where 12v meets).

Does that make sense ? Would hate to see something go pop.

db · Post by db » Mon Jul 14, 14 12:27 pm

My alternator has 3 as you say Morgan: BATT + and two marked FLD. When I first wired it up with the FBO boxes, it wouldn't charge. It only worked when I disconnected one FLD and connected it to earth.
I can leave the 'black box' in place if that will work?

db · Post by db » Mon Jul 14, 14 12:28 pm

Dave wrote:Your field wire just needs to hook up to the switched 12v source from your ignition switch.

I take it you have an internally regulated alternator?

No, I don't think it is.
Sorry, charging/ignition is something I struggle to grasp

Dave-R · Post by **Dave-R** » Mon Jul 14, 14 12:55 pm

Simple theory.
You move a wire through a magnetic field and a current is induced in that wire. The stronger the magnetic field OR the FASTER you move that wire, the more current is produced.

You can also hold the wire still and move the magnet instead.

The alternator will output voltage dependant on rpm. The faster it spins the higher the voltage output.

You only want 14.5 volts to charge the battery. So you have to regulate the output from the alternator so it does not go over that.

Regulators work by switching off the "field" in the alternator every time the output goes above 14.5 volts. On a mopar it does this by grounding the live field wire through the body of the regulator to the chassis on the car.

Every time the voltage goes BELOW 14.5 volts it switches the field back on again. It does this many times per second.

Without a regulator the alternator output would go sky high and boil your battery.

You would get very bright headlights though.